Rotary cutting device

ABSTRACT

A horticultural or agricultural cutting device is disclosed which comprises a body ( 4 ), a rotor ( 20 ) rotatably coupled to the body, at least one cutter ( 54 ), ( 56 ) which rotates along with the rotor and extends radially to the axis of rotation, and a powered drive (eg. an electric motor ( 40 )) which drives the rotor and cutter. The rotor provides a collection surface ( 58 ). ( 60 ) which follows the cutter as it rotates and so serves to collect cut material. The rotor is formed such as to expel the cut material centrifugally and the body provides a roughly tangential collection channel away from the rotor along which the collected material is thereby propelled. The collection channel is led to a waste receptacle.

CROSS-REFERENCE TO OTHER APPLICATIONS

This Application is a National Phase of International Application No.PCT/GB02/03889, filed on Aug. 22, 2002, which claims priority from GreatBritain Patent Application No. 0121447.7, filed on Sep. 5, 2001.

The present invention relates to, a rotary cutting device. The device inquestion may be for horticultural or agricultural use or mayalternatively be for use in food preparation.

The inventor's earlier patent GB 2266648B discloses a tool for use inthe garden, or in the workshop, which uses a rotating cutter juxtaposed(and in some embodiments integrally formed) with a helical rotor. Inoperation of the main embodiment described, cut material is collected byvirtue of the rotor and also propelled thereby, partly by the operationof the rotor as an archimedean screw and partly by flow of air producedby the rotor, along a path which is generally axial, with respect to theaxis of rotation of the rotor and cutter, to a collection receptacle.

The cutter/rotor combination proposed in the earlier patent has provento be highly effective. The construction of the device has however beendeveloped with two particular aims:—

i) to arrive at a device which can be formed as a well balanced, compactunit; and

ii) to avoid undue manufacturing cost.

In fact in developing the device a new principle of operation has beenarrived at which is considered to have a broad range of potentialapplications.

In accordance with a first aspect of the present invention there is arotary cutting device comprising a body, a rotor housed in the bodyadjacent an opening therein, the rotor being journalled upon the bodyfor rotation about an axis, and a powered drive mounted to the body forrotationally driving the rotor, wherein the rotor has at least onepaddle having a leading edge which extends radially with respect to theaxis and serves as a cutter, being exposed to the exterior of the bodyby virtue of the aforementioned opening so that it can be contacted withmaterial to be cut, the paddle also providing a collection surface whichfaces the interior of the body and follows the cutter as the rotorrotates, serving to collect cut material into the body, a wall of thebody encircling the rotor and having an opening leading to asubstantially tangential collection channel formed by the body, and therotor being formed such as to expel the cut material centrifugallywhereby the cut material is propelled into the collection channel.

The path defined by the body need not be at a precise tangent to therotating cutter and rotor. The essential point is that it must besuitable to receive material thrown centrifugally off the rotor. In thisrespect the present invention differs from the embodiments described inGB 2266648, wherein the archimedean screw action of the impeller drivesthe waste material along an axial path.

It has been found that the present invention makes possible a verycompact and attractive unit. The rotor of the present invention may alsobe designed for economical manufacture.

In an especially preferred embodiment of the present invention, thecollection surface is inclined, along the circumferential direction, toits plane of rotation such as to propel the cut material into the body.

Hence in this embodiment the collection surface moves the cut materialalong the axial direction, into the body, before it is tangentiallyexpelled by centrifugal action. The collection surface may even beformed as a helix.

Preferably, the collection surface is followed by an upstanding vanesurface by means of which the cut material is centrifugally expelled.

The cutting device is most preferably a horticultural or agriculturaldevice. Alternatively however the device may be for use in foodpreparation—enabling rapid slicing and collecting of foods.

The powered drive may be an internal combustion engine or a hydraulicmotor, although an electric motor is especially referred.

In accordance with a second aspect of the present invention there is arotary cutting device comprising a body, a rotor journalled upon thebody for rotation about an axis, and a powered drive coupled to therotor for rotational driving thereof, a pair of pinions being mountedupon the rotor on opposite sides of the rotor axis and a power drivensaw chain being led around the pinions to provide a chain saw whichextends radially with respect to the axis and rotates along with therotor.

Drive for the chain saw may be provided through a central drive gearengaged with the saw chain. The gear is most preferably co-axial withthe rotor.

Specific embodiments of the present invention will now be described, byway of example only, with reference to the accompanying drawings inwhich:—

FIG. 1 is a somewhat simplified and stylised vertical section through agarden trimmer embodying the present invention;

FIG. 2 is a perspective illustration of an essentially similar trimmerembodying the present invention, one half of a casing and also a wastecollection receptacle being omitted to expose parts of the mechanism ofthe trimmer;

FIG. 3 is a similar perspective illustration to FIG. 2 but omits afurther part of the casing in order to expose a rotor of the trimmer andother components;

FIG. 4 is a perspective illustration of a first rotor for use in thetrimmer, viewed from above and to one side;

FIG. 5 is a perspective illustration of the same rotor, viewed moreobliquely,

FIG. 6 is an illustration of a wheeled carrier with the trimmer mountedthereupon for use in trimming the edge of a lawn;

FIG. 7 is an illustration of an arrangement in which the trimmer ismounted upon an elongate handle;

FIG. 8 is a vertical section through a mini-trimmer constructed inaccordance with the present invention;

FIG. 9 is a plan, partly cut-away view of the mini-trimmer;

FIG. 10 illustrates the mini-trimmer in use;

FIGS. 11, 12 and 13 illustrate a larger and more robust embodiment ofthe present invention in use;

FIG. 14 is a perspective illustration of a further rotor and cutterarrangement for use in embodiments of the present invention;

FIG. 15 is a perspective, partly cut-away illustration of yet a furtherrotor for use in an embodiment of the present invention and of anassociated shroud;

FIG. 16 is a vertical section through the assembly shown in FIG. 15;

FIG. 17 is a simplified illustration of a brake mechanism used incertain embodiments of the present invention;

FIG. 18 is an illustration of an embodiment of the present invention inuse;

FIG. 19 is an enlarged illustration of selected parts of the embodimentseen in FIG. 18; and

FIG. 20 is an illustration of a lawn mower embodying the presentinvention.

In construction of the trimmer 2 illustrated in FIGS. 1 to 5, extensiveuse is made of injection moulded plastics. Other embodiments couldhowever be constructed using other materials eg. pressed sheet metal ordie cast aluminium.

The trimmer can be seen in FIGS. 2 and 3 to have a body 4 formed fromseveral plastics components. A handle portion 6 and arm portion 8 of thebody are both defined by a casing 10 which is vertically split into twohalves, joined together during assembly in the present embodiment byscrews (not shown, although screw holes 12 can be seen). At its endremote from the handle portion 6, the arm portion 8 is joined to agenerally annular shroud 14, formed as a separate plastics moulding. Theshroud 14 is outwardly tapered from top to bottom and has an upturnedlip 16 which contributes rigidity to this component. The shroud also hasan opening 18, through which cut material is propelled in use, as willbe explained below.

Contained in the shroud is a rotor 20 which will be described in moredetail shortly. The rotor 20 is mounted on a shaft 22 (as FIG. 1 shows)which is journalled in an upper bearing 24 mounted by the shroud andalso in a lower bearing 26 mounted by a cut away plate 28. The plate 28is itself mounted across the otherwise open, lowermost mouth 19 of theshroud 14 and in the present embodiment is cut away to provide acircular perimetral band 30 linked by radial spokes serving as staticblades 32 (see FIG. 3 in particular) to a central hub portion whichreceives the lower bearing 26.

Above the rotor 20 a rotor pulley 34 is fixed upon the shaft. A tootheddrive belt 36 couples the rotor pulley to a motor pulley 38 mounted onthe drive shaft of an electric motor 40 mounted in the handle portion 6of the casing 10. The rotor pulley 34 is of larger diameter than themotor pulley 38 so that the rotor 20 is driven to rotate more slowlythan the motor 40.

The use of a drive belt 36, extending through the arm portion 8, allowsfor a particularly well balanced, attractive construction. In use theweight of the trimmer is supported largely by means of a main handle 42,seen in FIG. 1 but omitted from FIGS. 2 and 3, projecting upwardly andforwardly from the handle portion 6. The heavy components—electric motor40 and the rotor 20 and its associated parts are on either side of thehandle and so balance each other. That is, by separating these partsusing the belt drive, the trimmer's centre of gravity is positioned ator near to main handle 42.

Turning now to FIGS. 4 and 5, the preferred form of the rotor can beseen to comprise two paddles 50, 52 each forming 180° of a shallowpitched helix. Thus, along the circumferential direction, the paddlesare both inclined to the plane of rotation. The leading, lowermost, edgeof each paddle is formed as a radially extending cutter. Morespecifically, in the illustrated embodiment, each of these edges 54, 56is sharpened to form a radially extending blade. While the rotor isformed of plastics, it is found that a sufficiently durable edge can beformed thereupon. Alternative constructions could use a metal bladeattached to the rotor, or in more robust embodiments possibly a pressedsteel rotor with a sharpened cutter edge. In fact the most preferredembodiment comprises a rotor principally formed of moulded plastics buthaving a sharpened metal leading edge 54, 56. These metal edges areincorporated in the rotor during the moulding process.

Uppermost surfaces 58, 60 of the paddles 50, 52 are referred to hereinas “collection surfaces” because they serve to collect material cut bythe blades 54, 56. These surfaces are, as can be seen, continuous withthe portion of the rotor forming the blades 54, 56. As the rotorrotates, the collection surfaces 58,60 follow the blades so that the cutmaterial rides up these surfaces and is thus collected. Following thecollection surfaces 58, 60 and again formed as integral parts of therotor 20, are upstanding vanes 62, 64. When the vanes reach the cutmaterial they cause it to move rotationally along with the rotor and thematerial is consequently also propelled radially outwardly bycentrifugal force. The effect is akin to a slingshot. When materialreaches the opening 18 in the shroud it is consequently propelled alonga generally radial path through the opening 18, along a short duct 66and so, into a waste collection receptacle 68 (shown in FIG. 1).

It should be noted that the leading edge of one paddle overlaps thetrailing edge of the other. This helps to prevent spillage of material.Thus the blade 56 is ahead of the vane 64, in the circumferentialdirection of travel, and likewise the blade 54 leads the vane 62 as therotor turns. The shape of the rotor also equips it to function as animpeller, drawing air into the body and in particular into thecollection receptacle 68. This movement of air assists in collection ofthe cut material.

The waste collection receptacle 68 is in the present embodiment providedby a plastics moulding mounted to the underside of the casing 10. It isremovable for emptying. FIGS. 2 and 3, from which the receptacle itselfis omitted, show a trigger catch 69 by means of which the receptacle 68is normally retained and by means of which the user can release it.

The cutting action of the blades 54,56 is to some degree assisted by thestatic blades 32 of the cut away plate 28, which tend to keep materialsuch as grass and hedge stalks in place as the blades move past toproduce the cut. However it has been found to be unnecessary for theblades 54, 56 and the static blades 32 to come into contact, and byseparating the blades 54, 56 upwardly from the static blades noise isreduced without impairing performance of the trimmer. The static blades28 need not be sharpened in order to perform their function.

Various designs of the blades 54, 56 may be utilised. They may forexample be curved, as viewed along the rotational axis, in the manner ofa scythe. Note that while the blades have been referred to as extendingradially, as they must, this does not imply that they must be actuallyparallel to the radial direction.

The static blades may take any of a variety of forms. They could forexample form a grid. The accurate spoke form seen in FIG. 3 is howeverconsidered advantageous in providing a shearing cut.

The trimmer illustrated in FIGS. 1 to 5 can be held in two hands fortrimming of hedges, long grass, etc. One hand holds the rearmost handleportion 6 to guide the device while the other hand holds the main handle42 to support its weight. Safety is of course an important design issue.In order to prevent the user from inadvertently inserting either handinto the rotating blades, the present embodiment is adapted to bring theblades to a halt in the event that the user releases either of thehandles 6, 42. A first switch is formed within the handle portion 6 andcontrolled by an elongate pad 80 projecting forwardly from the handleportion 6 (see FIG. 1). A second switch is controlled by a pad 82 whichis arranged to be grasped along with the main handle 42. Wiring of thetwo switches to the motor 40 is such that only when pressure is appliedto both pads 80, 82 is the motor activated. Preferably both switches arenormally “off”, being switched to “on” only by pressure applied to theirrespective pads, and are in series with each other.

The effect is that to activate the device the user must place one handon the handle portion 6 (and press its pad 80) and the other hand on themain handle 42 (and press its pad 82). Hence neither hand can be offeredup to the rotating blades.

Inertia tends to cause the rotor 20 to continue rotating after currentto the motor is switched off. To overcome this tendency the trimmerincorporates a brake mechanism which is released only when the motor isswitched on. For the sake of representational clarity the brakemechanism is omitted from FIGS. 1 to 5 but is illustrated separately inFIG. 17. It comprises a brake shoe assembly 84 within the rotor pulley34, the brake shoe 85 itself being a part circular member bearing anouter brake lining 86 and being pivotally mounted at 87. A spring 88urges the brake shoe 85 into contact with the inner surface of thepulley 34 to apply the brake and stop the pulley and hence also therotor 20. The brake is released by means of a solenoid 90 acting on theshoe through a flexible line 89 formed in the illustrated embodiment ofnylon. Tension in the line, produced by the solenoid in response topassage of electric current therethrough, pulls the brake shoe away fromthe pulley surface.

The solenoid is energised only when the motor current is on andtherefore stops the pulley 34 when current to the motor ceases, eitherbecause one of the switches is turned off or because of an electricalfailure.

In a more economical alternative construction (not illustrated) thesolenoid is dispensed with and the action of depressing one or other (orboth) of the switches causes the brake to be released, e.g. by means ofthe line 89 being led to one of the switch pads 80, 82.

The trimmer (or more preferably a more compact version of it, to bedescribed below with reference to FIGS. 8 to 10) can be used in trimmingthe edge of a lawn, and for this purpose is fitted to a wheeled carrieras illustrated in FIG. 6, wherein the carrier 100 itself is seen to havea wheel 101 (a skid could instead be used) coupled through an upright102 and a spacer arm 104 to an elongate handle 106. The trimmer itselfis indicated at 108, being mounted upon the carrier 100 with the axis ofrotation of the rotor generally horizontal. Hence the trimmer blades(not themselves visible in these drawings) face toward the edge 110 ofthe lawn in order to trim the lawn edge. The wheel supports and guidesthe trimmer as it is moved along the edge of the lawn.

In this configuration the waste collection receptacle 68 is notutilised. Instead the output from the duct 66 of the trimmer is ledthrough a flexible tube 112 to a separate waste receptacle such as abag. The separate receptacle, not itself illustrated, need not becarried along with the trimmer and so can have a larger volume than thewaste collection receptacle 68. The receptacle may for example be a bagplaced on the ground and connected to the trimmer through a flexibletube.

It is found that the air flow due to the impeller action of the rotor20, in addition to the slingshot effect of the rotor, serves to propelthe waste material along the tube 112. The air flow also assists byinflating the collection bag and so preparing it to receive material. Acollapsible tube, eg of thin plastics, may be used as this too isinflated in use by the rotor's impeller action.

A further configuration in which the trimmer, or a smaller, lighterversion of it, may be used is illustrated in FIG. 7. The trimmer is herelabelled 200 and is coupled, and inclined, to an elongate handle 202supporting a waste bag 204 to which the trimmer's output is fed. Herethe user, holding the handle 202, supports the weight of the trimmer andmoves it over ground to trim eg. long grass.

A further embodiment of the invention is illustrated in FIGS. 8, 9 and10.

This version is a mini-trimmer 300 to be held in one hand, preferably bymeans of a strap 302 as FIG. 10 makes clear.

The mini-trimmer comprises a casing 304 within which is mounted anelectric motor 306 whose power supply comes through a supply cable 308.While the mini-trimmer could be mains powered, the present embodiment ispowered from a separate battery pack 310 carried on the user's belt (seeFIG. 10) and connected to the trimmer through the cable 308. The batterypack also carries a switch which cuts off power to the mini-trimmer ifreleased. Hence the user must, as in FIG. 10, keep one hand upon thebattery switch while the other hand operates a further switch 311 on thecasing of the mini-trimmer. This is a safety feature, helping to ensurethat the user cannot injure a hand by bringing it up to the cutter ofthe mini-trimer while it is running.

The electric motor 306 carries a motor pulley 312 which drives a rotorpulley 314 through a toothed belt 316 and as before the motor pulley isthe smaller of the two pulleys, thus providing a speed reduction in therotor drive. Upper and lower bearings 318, 320 support a shaft 322carrying both the rotor pulley 314 and rotor 324. In this embodiment therotor has a twin-start, three-turn helix formed by a pair of helicalpaddles 326, 328 which terminate at their lower extremities in radiallyextending blades, one of which is seen at 330. A cut-away plate is shownat 332, being disposed at the otherwise open, lowermost mouth of thecasing 304. As before the cut-away plate serves as a fixed blade,enhancing the cutting action.

A path for conveyance of cut material away from the interior of thecasing 304 is provided through an opening 334 which leads via a shortduct 336 to a waste bag 338. In the illustrated embodiment the waste bagis slung beneath the user's arm but it could for example be carried inthe manner of a backpack, in which case a tube would lead from duct 336to the waste bag.

The mini-trimmer is well suited to light or precision work, such ashedge trimming or even topiary.

A larger and more powerful embodiment of the present invention isillustrated in use in FIGS. 11, 12 and 13. This version is a vehiclemounted trimmer for use eg. on farms or in parks for such tasks ascutting bushes, hedgerows and even young trees. The trimmer itself isseen at 400 and while its internal components are not illustrated theyagain comprise a rotor (formed in this embodiment of metal) providedwith cutting blades and arranged to centrifugally expel waste, whichpasses along a flexible duct 402 to a trailer 404 in the presentconfiguration. Drive for the rotor may in this embodiment be provided bya hydraulic motor driven from the hydraulic system of a tractor 408.

A hydraulically movable arm 406 carries the trimmer and preferablyallows the angle thereof to be hydraulically altered. The arm is mountedupon the trailer 404, drawn eg. by the tractor 408 to move the trimmeralong the hedgerow 410. The arm may alternatively be arranged on thehydraulic platform of the tractor.

A large and powerful version of this type of embodiment may be used infelling and processing trees, as FIGS. 12 and 13 make clear. The trimmer400 is first used to remove branches 420 (FIG. 12) and is then advanceddown the trunk 422 to reduce it to short logs which are, as beforecentrifugally expelled into a duct 402, formed in this drawing as arobust chute.

This embodiment has a rotor and cutter arrangement, illustrated in FIG.14, which does not utilise a blade as such to cut material. Instead thetwin-start, helical rotor paddles 502, 504 both carry a respective outersprocket 506. A chain saw 508 is led around both sprockets and is drivenby a central drive sprocket 510. The arrangement thus provides aspinning chainsaw to serve as the cutter and is therefore capable ofrapid and powerful cutting action. As before the rotor serves to collectcut material and to centrifugally propel it to a waste receptacle (notshown).

This rotor and cutter arrangement may alternatively be used in reducingfelled timber to wood chips, a log being fed onto the cutters (typicallyby its own weight, the rotor/cutter being mounted with cutters uppermostand the log descending onto it as it is converted to chips) and thechips being propelled by the rotor into a collection receptacle.

Still a further construction of the rotor is illustrated in FIGS. 15 and16. Here, the rotor 600 again has a twin start helix 602 terminating ina pair of cutting blades 604. Also seen in FIG. 15 is a radiallyextending fixed blade 606 formed by cut-away plate 608. As in previousembodiments the rotor is surrounded by a shroud, labelled 610 in thesedrawings, from which a collection channel or duct 612 extends forconnection to a waste receptacle.

In this embodiment however the helical rotor is surrounded at a lowerregion by a helical skirt 614. Consequently the rotor acts in the mannerof a true archimedean screw, the cut material being propelled in thisway upwards as the lower turns of the helix move past the material. Onlywhen the material is above the skirt 64 is the material thrown out ofthe rotor to the channel 612.

FIGS. 18 and 19 illustrate an alternative waste collection arrangementfor use with the trimmer 2 illustrated in FIGS. 1 to 5. In FIGS. 18 and19 the receptacle 68 has been removed and replaced by a bag 700 formedin this embodiment as an impermeable polythene bag fed through aflexible, thin walled extension hose 72 where mouth is clamped to theduct 66 by a tension ring 704, formed in this embodiment of rubber.Waste passes through the hose 702 to the bag 700, which provides alarger volume for receipt of waste than the receptacle 68. The bag 700and the hose 702 are inflated by air from the duct 66, helping to keepthe thin walled hose 702 clear for passage of material. However there isnot a throughput of air in the hose and bag, since both are impermeable.Feed of waste material is achieved here due to rotor's “slingshot”effect and by gravity.

FIG. 20 illustrates another embodiment of the present invention in theform of a lawn mower. A wheeled chassis 800 carries a pair of cuttingheads 802, 804 arranged side-by-side (ie laterally separated) and eachutilising a rotor of the general type seen in FIGS. 1 to 5 to cut grassand expel it along respective ducts 806, 808 which feed a common duct810 itself leading to a collection bag 812. The rotors (hidden from viewin the drawing by their respective shrouds 814, 816) share a powereddrive 818 which may be an electric motor or internal combustion engine.

1. A hand-held horticultural rotary cutting device comprising a body, arotor which is housed in the body adjacent an opening therein, and isjournalled upon it for rotation about an axis, and a powered drivemounted to the body for rotationally driving the rotor, the rotor havingexactly two paddles each having a leading edge forming a radiallyextending cutter exposed to the exterior of the body by virtue of theaforementioned opening so that the cutters are contactable with materialto be cut, each paddle forming at least 180 degrees of a shallow pitchedhelix and having a trailing edge, the leading edge of each paddleoverlapping the trailing edge of the other and so leading it as therotor turns, each paddle having a collection surface which is inclinedalong the circumferential direction to its plane of rotation, faces theinterior of the body, and follows the cutter as the rotor rotates andeach paddle having a vane upstanding from the collection surface, therotor having a circular outer perimeter and the body having a circularwall which encircles the rotor adjacent its outer perimeter and has anopening leading to a substantially tangential collection channel, sothat material cut by the cutter is caused, as the rotor rotates, to ridealong the collection surface and so be propelled into a region of thebody above the rotor, to be moved rotationally along with the rotor bythe vanes, and then to be centrifugally expelled into the collectionchannel for collection in a receptacle, the device further comprising aplate which is mounted across the opening in the body and is cut away toform multiple static blades which are adjacent the plane of rotation ofthe cutters, the rotor being journalled in an upper bearing mounted inthe body and a lower bearing, on the opposite side of the rotor from theupper bearing, mounted by the aforesaid plate.
 2. A device as claimed inclaim 1, wherein the rotor is shaped to function as an impeller,propelling air into the body.
 3. A device as claimed in claim 1, whereinthe powered drive is an electric motor coupled to the rotor by a beltdrive and housed in the body.
 4. A device as claimed in claim 3, havinga carrying handle formed by or coupled to the body at a region betweenthe rotor and the motor.
 5. A device as claimed in claim 4 for twohanded use, having a second handle formed by or coupled to an end regionof the body remote from the rotor.
 6. A device as claimed in claim 5wherein the said end region of the body houses the motor.
 7. A device asclaimed in claim 1 wherein the rotor and cutter comprise a unitaryplastics moulding.
 8. A device as claimed in claim 1, adapted to becarried and used one handed.
 9. A device as claimed in claim 1 which iselectrically connected to a separate battery pack for driving thepowered drive which is formed as an electric motor, the battery packcarrying a switch which stops the device if it is released.
 10. A deviceas claimed in claim 9 wherein the battery pack is coupled to a harnessby means of which the battery pack can be worn upon a user's body.
 11. Adevice as claimed in claim 1 mounted upon a wheeled carriage with anupstanding handle.
 12. A device as claimed in claim 1, wherein a skirtis provided which surrounds at least a lower portion of the rotor androtates therewith.
 13. A device as claimed in claim 1 comprising a pairof switches mounted at separate locations such that the user is requiredto use both hands to activate the respective switches in order toactivate the powered drive, which is de-activated upon release of eitherswitch.
 14. A device as claimed in claim 1 comprising a rotor brakewhich is automatically applied upon de-activation of the powered drive.15. A device as claimed in claim 1 which is a horticultural oragricultural device.